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A teenaged Kaidan Alenko was mulling over Jump Zero's isolation from the rest of the Sol system when his friend Rahna came up to him one day in 2168. The two developed a close bond during their stay at "Brain Camp" so when one of their mutual friends arrived bearing news about a transmitter for sending messages to Earth both of them went to check it out, reminiscing all the while. It had been at least half a year since both of them talked to their families as outside communication was prohibited, and Kaidan mused the reason for BAaT's distance from Earth was to prevent biotics like them from getting beat up by more normal folk.

The next day, Kaidan and Rahna were on the queue for water rations at meal break and discussing the events of the previous night. Kaidan sent a message to his parents with the makeshift transmitter, though he noticed that Rahna didn't and asked her why. Rahna claimed her parents would just turn them in and that she didn't know where her brother was, making communication pointless. Kaidan comforted her by opining the transmitter doesn't really work, though at that moment Commander Vyrnnus, one of their teachers, started ordering the cadets to assemble at the training room ASAP. As Rahna was terrified of the turian, Kaidan made more attempts to comfort her before going.

At the training room the students found a pile of building blocks on the floor and the transmitter's maker, Shelby, tied to a post. Vyrnnus lectured the cadets on how they were allegedly wasting their education, rhetorically asked if they thought it was a joke, and faced Kaidan in particular for an answer. Kaidan answered in the negative, as did the rest when the turian pressed them. Vyrnnus asked around if anyone knew what Shelby was doing the previous night, and when no one stepped forward, began establishing the rules of the biotic exercise involving the blocks at their feet.

Rahna was close to dropping from exhaustion several hours of continued biotic exercise later, though Kaidan managed to save her piece from falling. Vyrnnus noticed the gesture and moved towards the pair, where he praised Kaidan for the catch but began taunting Rahna with a glass of water biotically floated next to her. Kaidan and Rahna never got their water rations beforehand and she was sorely tempted to grab the glass, and Kaidan warned her not to. The warning came too late as Rahna already used her hand to reach the glass, and the turian biotically broke her arm for the "pathetic" gesture. This sent Kaidan into a biotic rage that knocked the turian backwards.

Vyrnnus engaged Kaidan in a biotic duel when he recovered from the initial blast, and Kaidan chose to employ defensive measures. When Vyrnnus drew a knife and sliced Kaidan in his right side, the human retaliated by blasting the turian again and jumpkicking Vyrnnus' head while he's down.

In the immediate aftermath a furious Kaidan looked over his shoulder and found the other students terrified at what he just did. Kaidan's mood swung from anger to horror when he saw that Vyrnnus has been killed. He tried to approach Rahna and ask if she's okay, though she was scared too and refused to let him near her.

At the day of Kaidan's departure from BAaT, he begged his guards in vain for a moment to bid Rahna goodbye, who weren't about to let him until Rahna showed up. Kaidan tried apologizing for his actions and Rahna understood the principle, but she maintained killing the turian didn't make things right. Kaidan angrily replied that Vyrnnus deserved it: even the administrators agreed he went too far with Shelby and her. Rahna would have none of it, though she apologized for being too scared of him. The guards tried to hustle Kaidan along saying time's up, though his temper and biotics flared as he was not yet finished talking to her. He returned his attention to his friend, only to see her waving goodbye and walking away.

One month later on Earth, Kaidan's father approached his son on the balcony of a high-rise offering beer and advice. Kaidan took the beer and listened to his father's words: he shouldn't be too hard on himself for doing what he thought was right, though even right choices have consequences. Not comforted by the words, Kaidan reflects there may not be a next time for him as he screwed up the BAaT opportunity, though his father professed faith in him finding one, bigger than anticipated. Kaidan stared at an incoming ship in the sky, and with a smile hoped his father was right.

Kaidan was born in 2151 into a family already familiar with space: his father served in the Alliance military. After his mother was downwind of a transport crash in Singapore, Kaidan was exposed in utero to element zero and beat the odds, gaining biotic potential instead of terminal brain cancer. At the time little was known about human biotics, but when the possibilities became better understood, a company called Conatix Industries was set up to track accidental eezo exposures. Children who showed enough potential to be worth augmenting with implants were 'encouraged' to attend BAaT (Biotic Acclimation and Temperance Training) which was conducted at Gagarin Station and nicknamed 'Brain Camp' by its attendees. As Kaidan tells Shepard, "[b]unch of guys in suits show up at your door after school. Next thing you know, you're out on Jump Zero."

Along with several other teenagers, including a beautiful, gentle girl named Rahna, Kaidan began his training but things went bad almost from the start. Conatix wanted to speed the work along and brought in an ex-military turian, Commander Vyrnnus, who was an expert in biotics but also a veteran of the First Contact War who disliked humans. Vyrnnus introduced himself by saying "I was at the helm of the dreadnought that killed your father", and Kaidan retorted that his father hadn't even been in the war. Vyrnnus had it in for Kaidan after that, and began pushing the teenagers very hard. Kaidan recalls: "You either came out a superman or a wreck. A lot of kids snapped. A few died."

Finally, the inevitable happened and Vyrnnus went too far. Rahna, who had become close to Kaidan during their training, reached for a glass of water instead of moving it biotically. Vyrnnus punished Rahna by breaking her arm and Kaidan tried to defend her, only to receive a beating from Vyrnnus. When the turian pulled a knife, Kaidan lost control and hit him with a full biotic kick, breaking Vyrnnus' neck. After Vyrnnus' death, BAaT was shut down and the records were sealed to hide the Alliance's mistakes. Though Rahna was safe from Vyrnnus, she was afraid of Kaidan after that and the two parted ways.

Kaidan dropped off the radar for a while to figure things out, feeling lost and paralyzed after Jump Zero, but eventually came back to the Alliance in 2173 — on his terms this time — because he wanted to serve. Refusing further biotic training or an implant retrofit, he enlisted in the Alliance Navy and worked his way up to Lieutenant, gaining several special commendations in the process despite the health problems he suffered with his L2 implants; these manifested as intense migraines that left him sensitive to bright lights and noise. Finally Kaidan was transferred to the SSV Normandy under Captain Anderson, where he later worked alongside Commander Shepard.

His experiences at BAaT and his long service make Kaidan politically savvy, but very conservative, cautious and self controlled. Originally, Kaidan was hesitant to use his abilities on living targets, but he changes his mind after seeing the destruction on Eden Prime. During the mission on Eden Prime, Kaidan was deeply affected by seeing his comrade and friend Richard L. Jenkins gunned down, his first friend lost in combat. Though he is a biotic, Kaidan's loyalty is to the Alliance and he has no sympathies for biotic extremists. He doesn't bear any ill-will toward alien races, not even turians, but says Vyrnnus made him see how "human" aliens are: that they're "jerks and saints," just like humans.

Kaidan also believes humans, as newcomers to the galactic community, shouldn't have a Council seat until they're ready for one, and that Ambassador Udina is doing more harm than good by pushing too hard. Shepard can discuss this with him and (if female) can even Charm or Intimidate Kaidan into becoming much more xenophobic and pro-humanity.

If asked, Kaidan can give feedback on recent missions, discuss the commander's decisions and give some insight into the crew's state of mind. Knowing they're going to be faced with difficult choices without reinforcements, Kaidan urges Shepard not to cut corners as Vyrnnus did, and always leave a way out to ensure nobody gets hurt further down the line. However, as the mission progresses Kaidan becomes concerned about the lack of backup from the Citadel Council. The evidence Shepard is gathering about Saren Arterius and the threat of the Reapers seems too much to ignore, but the Council just doesn't want to believe anything's wrong — proving 'human nature' carries across species.

During the operation at Virmire, Shepard can choose to save Kaidan's life at the cost of losing Ashley. Kaidan is an experienced marine who knows that Ash volunteered for the mission, but he's never lost a soldier under his command to hostile action. Kaidan becomes determined to make the Council listen to their evidence about the Reapers: if all the Citadel races rally to stop the machines, it will be a fitting tribute to Ashley.

If Kaidan goes with Shepard to Ilos, he is moved by the fate of the Protheans, knowing their sacrifice has given them all a fighting chance. Unless Shepard has persuaded him to adopt a more xenophobic view, during the assault on the Citadel he tells Shepard to save the Council, even though he knows it will cost many human lives.

If Shepard is female, Kaidan is attracted to her from the beginning. She tries to save him from the Prothean Beacon on Eden Prime and, thinking he triggered it when he got too close, blames himself for her suffering. He also slips up when he, Ashley and Shepard are taking in the view on the Citadel by inadvertently admitting he finds the Commander beautiful, much to Ashley's amusement.

When the Normandy is locked down by the Council, Kaidan offers Shepard his comfort and support, and they almost share a kiss before being interrupted by Joker. Once they are finally en route to Ilos, Kaidan goes to Shepard to talk about the mutiny and the upcoming battle, wanting her to know that he's enjoyed serving alongside her. After some prompting by Shepard, he finally lets go; from what he can see, everything else in the galaxy, even the Reapers, will come around again, but the two of them are what is important right now. Kaidan claims Shepard makes him feel human, and they can spend the night together, as long as nothing changes, and their duty to the Normandy's crew still comes first.

If Kaidan survived Virmire, he continued to serve under Shepard aboard the Normandy. During a routine patrol hunting for geth forces, the ship came under attack from a warship belonging to the enigmatic Collectors and Shepard forced Alenko to evacuate with the rest of the crew. Soon after Kaidan got the survivors out in an escape pod, the Collector ship fired again, destroying the Normandy and causing Shepard's death. Suffering from survivor's guilt at the loss of his ship and his commanding officer, Kaidan remained in the Systems Alliance, eventually coming to terms with his pain. Over time he was promoted to Staff Commander.

In 2185, Alliance colonies began vanishing en masse, and Alliance Command began to wonder if Cerberus was responsible. Kaidan also began hearing rumours that Shepard was alive and somehow involved with Cerberus, then received a tipoff that the human colony of Horizon might be the next target. Kaidan was dispatched to investigate, and began installing defense towers as a cover for his investigation into Cerberus. However he ran into hostility from the colonists, who didn't like Alliance involvement in their affairs. They believed the defence towers actually made them more of a target, and resented Kaidan's presence.

The tip paid off when Horizon was attacked by the Collectors, though they arrived before the defence towers were ready. Kaidan tried to defend the colonists but was stung by a seeker swarm and paralysed. Somehow he managed to shake off the effects and avoid capture by the Collectors, in time to be reunited with Shepard, who had raced to Horizon to save the colony and activated the defence towers to drive off the Collector ship.

Though initially pleased to see the Commander, Kaidan soon became wary of Shepard's involvement with Cerberus. He refused to entertain any thoughts of joining the mission, claiming he was an Alliance soldier and always would be, and that he could never trust Cerberus. He left to report to the Citadel, but warned Shepard to be careful.

If Kaidan died on Virmire, while searching the wreck of the first Normandy, Shepard will briefly see Kaidan's face in a flashback. The Galactic News may also mention that an Alenko Memorial Fund has been set up to send biotic children to the Ascension Project.

If Kaidan and Shepard had a romance in 2183, Kaidan takes her in his arms upon being reunited on Horizon, but his relief at seeing her alive soon turns to anger. He demands to know why Shepard didn't try to contact him and forced him to go through the pain of thinking she was dead for two years. He claims that working with Cerberus is a betrayal of everything they stood for, and leaves to report.

I'm sorry for what I said back on Horizon. I spent two years pulling myself back together after you went down with the Normandy. It took me a long time to get over my guilt for surviving and move on. I'd finally let my friends talk me into going out for drinks with a doctor on the Citadel. Nothing serious, but trying to let myself have a life again, you know?

Then I saw you, and everything pulled hard to port. You were standing in front of me, but you were with Cerberus. I guess I really don't know who either of us is anymore. Do you even remember that night before Ilos? That night meant everything to me... maybe it meant as much to you. But a lot has changed in the last two years and I can't just put that aside.

But please be careful. I've watched too many people close to me die -- on Eden Prime, on Virmire, on Horizon, on the Normandy. I couldn't bear it if I lost you again. If you're still the woman I remember I know you'll find a way to stop these Collector attacks. But Cerberus is too dangerous to be trusted. Watch yourself.

When things settle down a little... maybe... I don't know. Just take care.

--Kaidan

For her part, Shepard will keep a picture of Kaidan in her quarters, on her desk between her personal terminal and the Medal of Honor. Should Shepard choose to maintain the relationship with Kaidan, before going through the Omega 4 Relay, she will gaze at the picture before leaving. If Shepard becomes involved in a relationship with another crew member, she will eventually turn the picture face-down on her desk.

Kaidan returns to fight the Reapers, provided he survived on Virmire. If he did not, Ashley Williams will take his place in the squad. By the time of the events of the Reaper Invasion, Kaidan has been promoted to Major and commands the 1st Special Operations Biotic Company, a covert operations unit.

During the Reapers' invasion of Earth, Kaidan assists in evacuating Shepard from Earth onboard the Normandy SR-2. Kaidan then joins Shepard to a mission to recover Prothean data on Mars, where he displays great tactical and combat aptitude. However, he still does not fully trust the Commander, as he believes that Shepard may be a puppet for the Illusive Man. At the end of the mission, he confronts the Cerberus gynoid responsible for the base's destruction, but he is severely injured by it. He is taken to Huerta Memorial Hospital on the Citadel, where he slowly recuperates. While recovering, Udina offers Spectre status to Kaidan which he accepts.

Shepard will be able to speak to Kaidan by visiting him in the hospital after every major mission. If Shepard romanced Kaidan, then there is the option to continue the romance. In time, Kaidan recovers from his injuries and accepts Udina's offer.

When Cerberus invades the Citadel, Kaidan is tasked to protect the Councilors but is unaware that Udina and Cerberus are actually collaborating to take control of the Council. This puts Shepard and Kaidan in a conflict; Shepard must then convince Kaidan of the truth behind the attack.

Depending on past interactions with him, Kaidan can be talked down. If Shepard cannot persuade Kaidan to back off, Shepard, or one of Shepard's squadmates will kill Kaidan. If Kaidan lives past this event, he can either be recruited back into Shepard's squad on board the Normandy or left behind to provide assistance in the war. If made a war asset, Kaidan will send Shepard the following e-mail:

Good luck

From:Kaidan Alenko

Commander,

When I walked away from the Normandy, it felt strange. I knew leaving was for the best, but that didn't make it easy.

I just wanted to say, no matter what went down between us, I still consider my time on the Normandy to be one of the most important experiences of my life.

Take care of yourself, Commander.

And kick some Reaper ass.

Kaidan

If Kaidan is brought aboard the Normandy, he spends his time in the Starboard Observation Lounge. Immediately after coming aboard, Shepard finds him gazing through the observation glass at the starry background. Kaidan contemplates about the millions of people who are being affected by the war and is frustrated at not being able to save them all. He tells Shepard about his mother who has been separated from his father due to the war and is all alone in the crisis. Shepard can offer words of sympathy and tell him to be strong.

On retrieving the Prothean Javik from his resting place, aboard the Normandy Kaidan mentions that while he doesn't mean to sound unprofessional, he can't stop grinning at the situation.

After the Cerberus scientists have been rescued, Kaidan will ask to see Shepard in the Crew Quarters. He asks Shepard about an insight into Cerberus, about how the people involved could have changed from their nature in 2185. He also ponders on the Illusive Man, wondering how he could have changed from an ally to an enemy. Shepard replies that they never anticipated the sudden betrayal from Cerberus and advises Kaidan not to dwell too much on the Illusive Man as his crimes have gone beyond forgiving, regardless of what his past intentions were.

Later, Kaidan invites Shepard to lunch on the Citadel, saying that he needs a sanity check. If Shepard is not in a romance with anyone, Kaidan can make a pass the Commander at this point. Otherwise, he just expresses his admiration for Shepard and his consideration of Shepard as a good friend, to which Shepard can say that Kaidan is their brother.

Shepard and company embark on a mission to sabotage a gethdreadnought after receiving orders to enlist the quarians for the war. If Tali is around, after the mission Kaidan good-naturedly refers to her as a good egg and says he is glad to have her back on the team. On second thoughts, however, Kaidan tells Shepard not to tell her he called her an egg, in case it's a quarian insult.

If Shepard shuts down the geth servers on Rannoch by traveling into the geth consensus, Kaidan finds himself distracted on the mechanics of how such an interface could have worked. Working on a Spectre division expense report at the time, he tries to restrain his curiosity, but ends up asking Shepard what happened anyway, and gets regaled with a brief summary of what transpired. He later opines that entering the consensus is going to be the best chapter in the Commander's autobiography.

After the Battle for Rannoch, Kaidan is found playing poker with James Vega in the Port Observation Lounge. He doesn't seem to be able to compete with James, who plays poker regularly on the Citadel.

If Shepard sided with the geth, Kaidan remarks that the quarians' extinction was tragic and that he had always admired their resilience. If Tali survived until that fateful moment Kaidan says that he's sorry about Tali's death, remarks that she was "one of a kind", and he will miss her. He also says he'll never forgive the geth for Ashley and now Tali's deaths. If Tali died the previous year however, he wonders instead how history will remember the quarians.

If Shepard sided with the quarians, Kaidan will be glad that they are finally rid of the geth once and for all, stating that his experience with the synthetics mainly involved getting shot at.

If Shepard managed to unite the two races, however, he expresses his amazement at the negotiation Shepard pulled off, further stating that having both geth and the quarians on their side is a very good thing.

After the the fall of Thessia, Kaidan is found on the Engineering Deck with Engineer Adams, talking sympathetically about Liara, who just lost her homeworld. They reminisce about her stories she shared with them back in 2183 and hope that she remains strong. Kaidan also attempts to raise the Commander's dampened spirits by promising that Kai Leng will get his ass kicked next time.

After dealing with Henry Lawson's shenanigans on Horizon, Kaidan expresses his palpable anger through words, stating that the Illusive Man better say his prayers because now that the team knows where his base is they're coming after him. If Kaidan was among the landing party he says he's never been more filled with rage after what he saw there. Illusive Man is obviously crazy in his opinion, and in cases like Sanctuary, Kaidan wouldn't mind killing crazy.

After the mission to investigateLeviathan on Mahavid, Kaidan is disquieted at seeing the people on the asteroid trapped ten years in the past and wonders how many more people are trapped like that.

During the Battle for Earth, Shepard can speak to Kaidan. Kaidan reflects on his years of service as a soldier and thanks the Commander for being able to reach his present position as a veteran. He is disquieted at having to say his goodbyes to Shepard, to which Shepard can offer an opinion.

If Kaidan was left behind on Virmire, or killed during the Cerberus coup attempt, his name will appear on the Memorial wall aboard the Normandy.

Kaidan's presence during Shepard's shore leave adventures and beyond is contingent on him not being dead or sent to Admiral Hackett after the failed Citadel coup.

If Kaidan is romanced, he will be the first one to come to Shepard's aid during the ambush in the Wards. Otherwise he will arrive at the apartment with the rest of the squad.

After the conclusion of Shepard's clone fiasco, Kaidan can serve as back-up for the Commander during matches in the Armax Arsenal Arena.

Shepard can also invite Kaidan up to their Personal Apartment. When he arrives, he insists on cooking a meal of "beef, bacon and beer, the food of [his] people" for Shepard, guzzling a bottle with his Commander before starting.

If Shepard and Kaidan are lovers, the couple ask each other about their culinary skills. Shepard can either claim a roommate at Arcturus Station taught them to cook or claim expertise given time to practice, and Kaidan reveals that he learned to cook during his training with Conatix. Kaidan is distracted enough to burn the garlic on his recipe, and Shepard helpfully suggests hot sauce. After dinner the couple either can cuddle on the couch or go upstairs to "burn off" their calories.

If Kaidan and Shepard's relationship is platonic, Shepard verbally trashes Kaidan's cooking, playfully wary of any "food poisoning". The Commander either "threatens" to put him on kitchen detail with Adams for a month, or emphasizes how the close calls they had over the years is apparently nothing compared to Kaidan's cooking. Kaidan just shakes his head and responds with indignation. After the dinner Shepard can admit approval at the meal, in which case Kaidan conflates his kitchen skills with winning a fight with James, or continue bantering with Kaidan in a friendly manner, accusing each other of being too "sensitive."

Despite being on Shepard's team, Kaidan is an optional invite to the Commander's big party. During the first part of a loud party, he can be found with James and Steve. If Jack is present, Kaidan will remind her to keep her biotics under control. If she is not present, Kaidan will be the one to answer the question of what happens when a biotic gets drunk, saying it's just like everyone else except he glows blue when he does it. Steve will tease Kaidan about being a cheap date and asks about biotic party tricks, which Kaidan says are much more impressive when the audience is also drunk.

Kaidan can be found in the same place in the first stage of a quiet party, agreeing with Jack about not trusting Cerberus, and suggesting that the party get a bit crazier. If Wrex is present but Jack is not, he and Kaidan will reminisce about Ashley.

During the second stage of an energetic party, he can be found with Liara and James in their argument about biotic versus physical superiority. When James makes a jab about "flawed implants" Kaidan will shoot back with how hard he's worked and his resulting ability to Reave, to Liara and possibly Jacob's confusion. If Shepard sides with physical superiority , Kaidan will be flabbergasted, prompting Shepard to comfort him by saying that Kaidan's kind of physical excellence is still Shepard's kind of physical excellence. Kaidan will eventually confirm for James that as a child he frequently threw things around with his biotics.

During the second stage of a quiet party, he can be found with Joker and Samantha on the second floor. While they are discussing EDI, Kaidan will bring up the time her body almost killed him. Later, Joker will ask the long burning question of how Kaidan gets his hair to stand up like that; it's static buildup from his implants.

During the last stage of a loud party, Kaidan can still be found on the balcony. If Shepard sided with biotics in the earlier argument, Kaidan will request a turn demonstrating biotic superiority on James. If Shepard sided with physical ability previously, he will be winning against James in a pushup contest with Liara rooting for him. In both cases, that group will then start dancing afterward.

In the last stage of a quiet party, if Shepard chose preparing food in an earlier argument between EDI and Steve, Kaidan will be found in the kitchen with EDI and Samantha. At first he will be arguing with EDI about the amount of curry that should be used, and ends up offending Samantha when asking her help to make his point. When the group discusses the team dynamics of a party, EDI rules out Kaidan as the mingling specialist due to an occasional tendency to be judgmental. If Shepard chose making drinks in the earlier argument, Kaidan and his group will be found at the bar instead, with Samantha serving as bartender. Kaidan is nonplussed to learn that the frozen Pyjak Samantha gave him was comprised of the contents of her spill pad.

During the photo, Kaidan will be next to Shepard if he is romanced, and in the middle row if he was not.

If Kaidan was romanced, he and Shepard will wake up in each other's arms the next morning. Regardless of relationship status, he can then be found in the kitchen saying what a great time he had and rapidly demanding coffee.

If romanced, Kaidan will be the one to talk to Shepard while returning to the Normandy. He'll tell Shepard that he trusts them to find a way to win and promises to be waiting. He calls everything they've been through the "greatest challenge of [his] life", as well as calling it "the greatest reward." Kaidan will also say that it's been "a good ride," to which Shepard will respond, "[t]he best."

A female Shepard who romanced Kaidan in 2183 has differing dialogue with him during the mission to Mars, where they discuss their relationship, and Kaidan's fears that she is no longer the woman he loved. She can either be consoling or confrontational.

While in the hospital, Kaidan will send a message to Shepard asking to meet with her. If Shepard romanced another person in 2185, Kaidan will ask her about it, where she can either apologize, explain herself, or lie. Lying will make Kaidan angry and he will order her out of the room, although she has the chance to admit her lie and apologize. If she apologizes or attempts to explain, Kaidan remarks that he still cares about her, and there is no other woman in his life. Buying Kaidan a bottle of TM-88 Peruvian Whiskey from the Sirta Supplies store will cement their relationship further.

If Kaidan joins the crew after the Cerberus attack on the Citadel, Shepard can resume a romance with him, or start a new one if she did not do so before. He invites the Commander out for a drink at Apollo's Cafe, where he reminisces that he often had a few beers at his parents' home overlooking English Bay in Vancouver. He'll reflect on their relationship, and wonders if they have a future together. He'll also forgive her for cheating on him. Shepard can pursue the relationship by telling him that she loves him.

If Kaidan was not romanced in 2183, either a male[1][2] or female Shepard can start a new romance with him in 2186. They can do so by visiting him in the hospital, picking him up a bottle of whiskey from the Sirta Supplies store, and locking in the romance when Kaidan talks about how he never looked for a relationship before while at Apollo's Cafe.

Before the final battle, Kaidan will show up at Shepard's quarters offering "a quick drink". If playing a female Shepard who has rekindled a relationship with him, they will briefly discuss their first night together; otherwise, they will discuss the battle and their feelings before Kaidan admits that he didn't come for a quick drink.

During the final mission on Earth, Shepard can say their goodbyes to Kaidan. Kaidan will talk how he lived an amazing life thanks to Shepard and how hard he will fight so that he could hold Shepard again. If Kaidan is with Shepard in the final push to the Conduit, and if Shepard has mustered enough of the galaxy's forces, he will be badly injured by Harbinger's beam and will be evacuated to the Normandy. Shepard and Kaidan will profess their love for each other before Shepard goes to the Citadel beam.

If Shepard decides to fire the Crucible and Kaidan survived the final battle, he will be the one to put Shepard's name on the Memorial Wall or if the galaxy's military strength is sufficient and the Reapers are destroyed, he will refrain from putting Shepard's name on the Memorial and smile. If Shepard merged organics and synthetics, after placing Shepard's name on the Memorial Wall, Kaidan will share a hug with EDI.

If Shepard has any biotictalents, Kaidan will claim that though his abilities spike higher than most L3s, Shepard is the exception, indicating that the Commander is an L3. This appears to occur regardless of Shepard's class.

On the PS3 version of Mass Effect 2, if Kaidan died on Virmire, his picture may appear in Shepard's cabin even if he was not the chosen love interest in Mass Effect: Genesis, possibly caused by a glitch in the game.[4]

His name is sometimes spelled "Kaiden" in external media (such as the Character Spotlight) and even in-game at least once, in the subtitles on approach to Virmire.

As part of a workaround for a programming issue, Mark Meer voiced all of the lines for the Kaidan romance in Mass Effect even though the romance was intended to be exclusive to female Shepard.[5] It is possible for a male Shepard to have a romance with Kaidan through the use of save edits, although some of the dialogue options are missing and Kaidan's dialogue will occasionally refer to Shepard as female.[6]

When Kaidan is encountered in the opening for Mass Effect 2, he is wearing Heavy Armor; and later on Horizon, he is wearing Medium Armor. However, in Mass Effect, he could only equip Light Armor.

On November 24, 2011, Raphael Sbarge, as a Thanksgiving Day present, released a sound file where he voices Kaidan's apology email to Shepard in Mass Effect 2 after the two meet on Horizon. The sound file was later taken down but was rereleased on YouTube.

The surname "Alenko" suggests Ukrainian origin; surnames ending in "enko" usually are. "Alenko" would mean "the son of Al". In Ukrainian language, the word "kaidan" ("кайдан") means "a shackle".

Numerous interactions with Kaidan in Mass Effect 3 (his date with Shepard, during a poker game after Rannoch, and during Shepard's party at Anderson's apartment) suggest he's of Canadian nationality. Canada has a very large Ukrainian diaspora.

As with all squad members, Kaidan has unique dialogue that can be heard at various locations, during missions or assignments, or if a specific squad member is in the selected team.